Are you choosing the right timber for your project based on its durability and treatment?
Often when selecting a timber for a job, the price is a factor for your customer. But if you base it solely on price, it may not necessarily be fit for purpose for your specific job if you don’t consider the durability of the timber and the exposure hazard level of the situation.
The more durable timbers, like a hardwood species such as ironbark, are often at the pointy end of the price range, due to their suitability for a variety of conditions that require a higher durability. The price variance could be due to a number of factors like demand/supply pressures or additional supply processing costs. Sometimes cheaper timbers can be a durable option when they have the appropriate treatment.
The most common wood preservative treatments that you will see through NHS are:
- Chromated Copper Arsenate (CCA)
CCA has been the main type of treatment for many years. The durability of this product is attractive but should be noted that in Australia it can’t be used in high contact with children, e.g. play equipment or residential decking. (see apvma.gov.au/node/11751 for a more detailed listing). So generally you will find these in sleepers and logs at NHS and occasionally in larger end sections of treated pine due to availability issues. - Alkaline copper quaternary (ACQ)
ACQ is an arsenic-free treatment and like CCA provides protection similar to CCA. The popular treated pine commodity decking is ACQ treated. - Light Organic Solvent Preservatives (LOSP)
One of the newer technologies, LOSP has some advantages in the drying aspect, which means a faster turnaround into a building yard like ourselves. This treatment type can be found in the structural timbers and primed timbers.
In addition to treatments, you should also note the hazard level which defines the exposure suitable for the application. The most common hazard classes locally are:
| Hazard Class | Exposure | Service Condition | Hazard | Example uses |
|---|---|---|---|---|
| H1 | Inside above ground | Completely protected from the weather, well ventilated and protected from termites | Borers | Susceptible framing, flooring, furniture, interior joinery used across Australia |
| H2 | Inside above ground | Protected from wetting, no leaching. | Borers and termites | Framing, flooring, furniture, interior joinery used across Australia |
| H3 | Outside above ground | Periodic moderate wetting and leaching | Moderate decay, borers and termites | Weatherboards, fascias, pergolas, framing etc. |
| H4 | Outside inground | Severe wetting and leaching noncritical applications | Severe decay, borers and termites | Fence posts, retaining wall less than 1 m high, landscaping timbers. |
| H5 | Outside inground with or in fresh water | Extreme wetting and leaching, critical application | Very severe decay, borers and termites | Piling, house stumps, power poles cooling tower fill, building poles, retaining walls more than 1m high |
| H6 | Marine waters | Prolonged immersion in sea water | Decay and marine wood borers | Boat hulls, marine piles, jetty cross bracing, jetty landing steps |
Follow all requirements for safe handling and remember treated timbers should not be burnt or used as sawdust around your pets. We have a range of safety equipment available to help you with your job.
You can refer to http://www.tpaa.com.au/timber-treatment/ for more information on specific timber treatments.
As always, come in and chat to one of our friendly team members who can discuss the right timber for your project! Contact us
